Reduction of nitro compounds.



736,205. PATENTED AUG. 11, 1903.

M. BU-CHNBR.

REDUCTION OF NITRO COMPOUNDS. APPLICATION rum) SEPT. 24. 1900.

N0 MODEL.

[NVENZOR WITNESSES.-

mmz m/ 7 UNITED STATES Patented August 11, 1903.

PATENT FFICE.

MAX BUCHNER, OF MANNHEIM, GERMANY, ASSIGNOR TO 0. F. BOEHRINGER & SOEHNE, OF MANNHEIM-WALDHOF, BADEN, GERMANY, A FIRM.

REDUCTION OF NITRO COMPOUNDS.

SEIECIFIGATION forming part of Letters Patent No. 736,205, dated August 11, 1903. Application filed September 24, 1900. Serial No. 30.969. (No specimens.)

.[ all whom it may concern.-

Be it known that 1, MAX BUOHNER, a citizen of the Empire of Germany, residing at Mannheim, in the Empire of Germany, have invented certain new and useful Improvements in the Reduction of Nitro Compounds, and I do hereby declare the following to be a full,

7 clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. a

This invention relates to the reduction of nitro compounds, with particular reference I to the employment of an electric current for of tin, the tin being in acid solution.

such purpose. 7

In my Letters Patent of the United States No. 700,670, May 20, 1 902, I have described aprocess of electrolytic reduction of nitro compounds, which consists, essentially, in causing an electric current to pass through the nitro compound placed in the cathodespace of an electrolytic cell in the presence Under that process the reduction of the compound employed and the recovery of thetin employed take place simultaneously. In the course of my-further experiments and researches in this direction I have found that this method may be carried out also by means of lead, mercury, chromium, or iron, and my invention consists in the reduction of nitro compounds by causing the electric current to I pass through such compounds in acid solution ber. I In both cases the reaction proceeds over or by way of the regenerated or recovered metal or metal ion. There exists in the two cases merely a difference in the form of regeneration of the metal. or metal salt, which form is governed by the magnitude of the electrolytic-solution tension of the element in question. If the same is small, the metal after having entered the ion condition and thus carried out the reduction is directly restoredto the metallic from the ion condition. If, on the other hand, the same is great, the metal is not regenerated, but only the ion of a lower valency- -for example, in the case of iron the Fe of the ferric chlorid can only be regenerated to the ferrous condition of Fe in the lower chlorid.

I will now describe my invention in. detail with the aid of several examples embodying what I consider the preferable method of carrying the same into effect.

1 Reduction of iiitrobenzene by the addition of lead chlorid to the cathode electrolyte-An electrolytic element or battery is divided into a cathode and an anode chamber by a suitable diaphragm. The electrolyte of the anode-space consists of a ten-per-cent. solution of sulfuric acid, the anode consisting of any suitable indifferent metal. The cathodechamber contains a cylindrical platinum electrode and is charged with a mixture of five hundred parts, by weight, of fuming hydrochloric acid; five hundred parts, by weight, of water; one-hundred and twenty-five parts, by weight, nitrobenzene, and fifty parts, by weight, of lead chlorid. The nitrobenzene is maintained in suspension by a rapidly-revolving agitator or stirrer and when consumed is replaced by a fresh supply, thus making the process continuous. During the course of the process the mixture is preferably cooled. The current introduced has a density of about nineteen hundred amperes per square meter, and this'current is. main tained until regular liberation of hydrogen takes place and becomes visible. After the process of electrolysis is completed the lead of the lead chlorid will be found to have been separated in the form of fine metallic sponge finely-divided metallic lead are added to the cathode electrolyte.

3. Reduction of mltrobenzene by addition of ferrous chlom'd to the cathode electrolyte. The conditions and proportions of the ingredients of the bath-reducing salt and the subtance to be reduced are the same as under Example 1 in this application and in my Patent No. 700,672, May 20, 1902. The current density is also the same. In this case, however, no metallic iron, but only ferrous chlorid, is regenerated.

When employing the other metals herein-- above referred to, the conditions and proportions and the amperage per unit of surface remain substantially the same, the proportions being somewhat modified, of course, where the metal is used instead of its salt, as indicated in Examples 1 and 2.

In the accompanying drawing I have represented one out of many of the possible forms of apparatus and electrolytic cells for carrying out the process involved in my invention.

In the drawing, A represents the anodechamber, containing the anode electrolyte, and athe anode; O, the cathode-chamber, containing the cathode electrolyte, and c the cathode, while at represents a diaphragm of any suitable material for separation of two electrolytes, as will be readily understood.

S represents a suitable stirrer arranged within the cathode electrolyte, the spindle or shaft 3 of which may be connected with any suitable source of power by a belt and pulley B P, as shown, or otherwise.

The cooling of the cathode-compartment may be carried out in any well-known manner, such as by cooling-coils and the like.

What I claim, and desire to secure by Letters Patent of the United States, is

1. The process of reduction which consists in introducing the reducible substance into a cathode electrolyte of hydrochloric acid and passing an electric current through the same in the presence of chromium.

2. The process of reduction which consists in introducing the substance to be reduced into a cathode-bath containing hydrochloric acid and a compound of chromium, and passing an electric current through the same.

The process of reduction which consists in introducing the reducible substance into a cathode electrolyte of hydrochloric acid, and passing an electric current through the same in the presence of chromium, and, at the same time stirring and cooling.

I Y 4. The process of reduction which consists in introducing a substance reducible to an amin into a'cathode-bath containing hydrochloric acid and passing a current through the same in the presence of chromium.

5. The process of reduction which consists in introducing a substance reducible to an amin into a cathode-bath containing hydrochloric acid and passing a current through the same in the presence of a chromium cathing a current through the same in the presence of chromium. v

8. The process of reduction which consists in introducing the substance to be reduced into the electrolyte contained in the cathodespace of an electrolytic cell and passing a current through the same in the presence of a chromium cathode.

9. The process of reducing a nitro compound which consists in introducing such compound into the electrolyte of the cathodespace of an electrolytic cell and passing an electric current through the same in'the presence of a chromium cathode.

10. The process of reduction which consists in introducing the substance to be reduced into a cathode-bath containing a compound of chromium and passing an electric current through said bath.

11. The process of reduction which consists in introducing the substance to be reduced into the cathode electrolyte and passing an electric current through the same in the presence of chromium and at the same time stirring and cooling.

12. The process which consists in introducing a substance Which is reducible to an amin into an acid cathode-bath in which is arranged a chromium cathode and passing an electric current through the same.

In testimony whereof I affix my signature in presence of two witnesses.

MAX BUCHNER. Witnesses:

JAcoB ADRIAN,

FRITZ A011. 

